There are various applications in which valves are used for controlling fluid and where it is desirable to lock the valve in a predetermined position so that no one can tamper with or inadvertently change the valve control of the fluid flow. Dispensing valves have been provided for this purpose which utilize a regular key adapted to be turned in a lock to open and close the dispensing valve to which the lock is attached.
Among the problems encountered with such prior art lockable dispensing valves are the effects of pressure from the fluid on the closed valve or the build up of deposits in the valve housing resulting from the fluid flowing therethrough, which may hinder or inhibit operation of the valve by means of the key.
Such balky valve operation encourages too much force on the key which can snap the key off the lock, possibly resulting in the destruction of the valve in trying to extract the broken key. Another problem is turning the key too far, which can damage the valve or strain the key, such that repeated overturning, twisting of the key shears it off in the lock.
Furthermore, in the operation of the key, particularly if the lock is stuck or is difficult to manipulate with the key, it may be possible to turn the key to such a position that the valve is partially open or closed with the key either left in or removed from the lock, thereby resulting in an indeterminate valve setting. With such a locking valve it is intended that the valve be completely open or fully closed, when the key is removed, so that the valve will function in a predetermined manner under the sole control of the authorized operator who has responsibility for use of the key.